The present invention relates to the general field of devices for controlling fluid flowrate and it is more particularly concerned with a self-cleaning metering device.
It is known that in valves used for regulation, the operational guidance lengths give rise to friction which then generates a hysteresis phenomenon. This friction is all the greater since the contamination which exists in any fluid causes the creation of xe2x80x9cgumsxe2x80x9d on the contacting guiding surfaces.
In the particular case of the metering devices of fuel injection systems, in turbojets or turboprops (more generally referred to as turbomachines), this hysteresis causes a heterogeneity of the injection flowrate which could impair the proper operation of the turbomachine, especially at the time of switch-on thereof.
A solution to this problem conventionally consists in reducing the frictional surface areas. However, this solution has the major drawback of increasing the contact wear of the remaining operational surfaces and therefore of limiting the lifetime of the metering device. Another solution consists in reducing the coefficient of friction of the contacting surfaces. However, here again, this solution proves to be inadequate when the build-up of gums or/and of contaminants becomes too large.
It is therefore an object of the present invention to alleviate these drawbacks by proposing a fluid metering device which makes it possible to appreciably reduce or even to eliminate any build-up of contaminants due to the movement of the fluid through the device.
These aims are achieved by a fluid metering device for metering a fluid from a supply source to means of use of this fluid comprising a metering valve able to slide in a sleeve over a travel C, the said valve comprising an intake orifice for admitting the fluid from the said supply source and an orifice for ejecting this fluid to the said means of use, characterized in that it comprises means of channelling the fluid intended to allow, during the movement of the metering valve in its sleeve, a sweeping of the fluid over all the contacting surfaces of the said valve and of the said sleeve.
With this particular structure, the fluid is compelled to sweep all the contacting surfaces. Self-cleaning of the device is thus ensured, thereby preventing the build-up of contaminants, and the creation of xe2x80x9cgumsxe2x80x9d, by discharging them with the metered fluid.
Advantageously, the means of channelling the fluid comprise a helical groove of width L and of pitch P.
According to the embodiment envisaged, the means of channelling the fluid may be disposed on the said metering valve or on the said sleeve.
Preferably, the travel C of the metering valve is greater than or equal to the distance Pxe2x88x92L.